Input: ep93xx_keypad - switch to using managed resources

By using managed resources (devm) we are able to streamline error handling
in probe and remove most of the custom remove method.

Acked-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Link: https://lore.kernel.org/r/YWZGKWgdarGtvtYA@google.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>